Behold another rant on nomenclature, posted on the Dinosaur Mailing List recently. I am slightly modifying it for consumption here.

There is a persistent use of the term “microraptorine” in reference to a subset of “deinonychosaurs;” these small theropods, including the “four-wing” form and a host of small-bodied an very gracile animals with long limbs, and a unique L-shaped pubis when viewed laterally bearing a high lateral flange, are useful as a grade of basal “deinonychosaurs” that, depending on the phylogeny, have been placed outside a grade including “unenlagiine” and “dromaeosaurid” deinonychosaurs, or closer to “dromaeosaurids” than to “unenlagiines.” I discussed this to some degree here, where the issue of what you name this particular clade comes up.

Microraptoria was named by Senter specifically as a non-ranked clade name. Despite this, use of “microraptorines”, “Microraptorinae” and so forth has persisted despite attempts to clarify. It does not help that Longrich & Currie (2009) thoroughly use the heck out of “Microraptorinae” while attributing this to Senter and co., when they coined a different name entirely. So when Wikipedia redirects links to Microraptoria to “Microraptorinae,” even going so far as to cite Longrich and Currie (in naming Hesperonychus elizabethae) for a “Microraptorinae” within “Microraptoria” you tend to think they are actually supported in this action, but clearly skipped over the specifics on this point.

Figure 3 from Longrich & Currie (2009), with “Microraptorinae” in a green box, and the name is in a box of deeper green.

The sister clade to Dromaeosauridae sensu stricto is speciose enough to warrant its own generic name. We therefore introduce the name Microraptoria, defined as the clade of taxa that are more closely related to Microraptor than to Velociraptor or Dromaeosaurus. We have deliberately avoided the suffices “=idae” and “-inae” for this name. Under a phylogeny in which Troodontidae and Dromaeosauridae are sister taxa, and Sereno’s (1998) nomenclature has priority, “Microraptoridae” would occur within Dromaeosauridae, engendering confusion by yielding the appearance of a family within a family. Under the phylogeny recovered here, “Microraptorinae” would occur outside any taxon with a name ending in “-idae”, engendering confusion by yielding the appearance of a subfamily without a family.

Longrich and Currie, rather, consistently use “Microraptorinae” where Senter et al. provided for “Microraptoria,” even citing Senter on the nomenclature. I’d rather approach this as a lapsus rather than a fault, and suspect they meant to use Senter’s word but were understandably mistaken on its treatment due to the unusual case of placing a non-ranked clade name within a “family” grouping of taxa.

Figure 2 from Senter et al., 2004. Microraptoria is in green, and the name is in a box of deeper green.

I note that similar issues correspond to the effect of further phylogenies shuffling around taxa like Unenlagia comahuensis and its apparent sister taxa, and their relationship to troodontids, dromaeosaurids, or even specific subgroupings of the latter “collective” (which i note here under the “family” name merely due to gradient). Under the rules of the International Commission on Zoological Nomenclature, this is not a problem, since the convenience is that a systematist who first names one Family-rank taxon names ALL of them, meaning there is always a convenient name available. There is a further problem, in that occasionally, you get “subfamilies” in families that do not contain taxa not contained by another “subfamily,” an effect that has resulted from the argument that certain ranks with diagnoses are true always (until otherwise defined), meaning you can pretend that a “family” is true only for a subset for which it is initially built to include.

I recently mentioned this problem with regard to “a new family of amphibians” (the conversation about this starts here, is replied to by [recently Dr.] David Marjanović here, and persists until here — including my apology for calling these “amphisbaenians”). The issue, perpetuated in the original literature, is that there is a concept of a “fixed” idea for a clade name with attached to a rank — it is, in fact, the only way to justify the existence of ranks: to agree that the diagnosis or definition will always be true … unless, of course, someone wants to “revise” it…. This seems to be a mentality, a sort of “Linnaeism,” that decides a rank must exist, and enforces this on nomenclature regardless of the existence of a counterargument, or even in defiance of the original argument (as in Longrich and Currie’s discussion). It was this problem that caused virtually every bird, fish and mammal to be diversified each into its own family-ranked taxon, regardless of how few species were present, as well as “suborders”; it allowed systematists to claim a “new bird” was so distinct, it had to have a new family and suborder for it, so that it was “equivalent” to all of the other groups of birds. This issue persists today, and will continue to persist.

The way things were done before is not tenable. The changing world requires that we find ways to talk about groups of taxa that we cannot simply shoehorn into classic ranks or subranks. There simply aren’t enough of them, despite the attempts of some to go overboard in applying various prefixes or suffixes to other names in order to “rank” everything. They’ll run out of those. The alternative, while staying in rank-land, is to simply ignore the issue (as when dealing with diversity in and among “species groups”). Removing ranks removes this problem: if a node or stem is useful to discuss, name it, use it, and move on.

[n1] Title quote is from The Princess Bride, specifically the trope wherein Inigo Montoya indicates to Vizzini his use of “Inconceivable!” is not relevant.